The invention relates to an arrayed waveguide grating device, a process for producing the same, an arrayed waveguide module, and an optical communication system. More particularly, the invention relates to an arrayed waveguide grating device, which can correct the wavelength to be selected, a process for producing the same, and an arrayed waveguide module and an optical communication system using said arrayed waveguide grating device.
An increase in capacity of data to be transmitted has led to a demand for further increased transmission capacity in an optical fiber communication system. For this reason, optical wavelength filters are becoming increasingly important as multiplexing/demultiplexing devices for dividing or multiplexing wavelengths by dense wavelength division multiplexing (DWDM).
There are various types of optical wavelength filters. Among others, arrayed waveguide gratings have a high extinction ratio in narrow band wavelength characteristics and can also function as a multi-input/multi-output filter device. Therefore, the separation of multiplexed signals and the multiplexing of separated signals are possible, and, thus, advantageously, a wavelength multiplexing/demultiplexing device can be easily constructed. Further, when an arrayed waveguide grating device is constructed by a quartz waveguide, the efficiency of coupling to optical fibers is high and low insertion loss operation with an insertion loss of about several dB (decibels) can be realized. By virtue of this, arrayed waveguide gratings have drawn attention as a particularly important device among the optical wavelength filters, and have been energetically studied in Japan and other countries.
FIG. 1 shows the whole construction of a conventional arrayed waveguide grating. An arrayed waveguide grating 11 comprises: a single or plurality of input waveguides 12 provided on a substrate (not shown); a plurality of output waveguides 13; a channel waveguide array 14 of channel waveguides bent in a certain direction with respectively different curvatures; an input-side slab waveguide 15 for connecting the input waveguides 12 to the channel waveguide array 14; and an output-side slab waveguide 16 for connecting the channel waveguide array 14 to the output waveguides 13. The course of multiplexed signal lights introduced through the input waveguides 12 is widen by the input-side slab waveguide 15, and the multiplexed signal lights are incident as equal phases on the channel waveguide array 14. The incident light intensity varies depending upon incident positions of the input-side slab waveguide 15. Specifically, the closer the incident position to the center portion, the higher the intensity The intensity distribution is substantially a Gaussian distribution.
In the channel waveguide array 14, a certain optical path difference is provided among the arrayed waveguides constituting the channel waveguide array 14. The optical path lengths are set so as to be successively increased or decreased. Therefore, a phase difference is provided at certain spacings in the lights guided through the arrayed waveguides, and, in this state, the lights reach the output-side slab waveguide 16. In fact, due to wavelength dispersion, the equal phase face is inclined according to the wavelength. As a result, light image formation (focusing) take place at different positions at the interface of the output-side slab waveguide 16 and the output waveguides 13 according to wavelengths. Since the output waveguides 13 are disposed at positions corresponding respectively to the wavelengths, desired wavelength components can be taken out of the output waveguides 13.
The center wavelength of this type of arrayed waveguide grating 11 is very sensitive to a change in refractive index of the waveguide material. Therefore, a variation in the film formation process as the production process leads to a change in the center wavelength, This in many cases makes it impossible to obtain values as designed. The change in center wavelength poses a problem that optical loss at the wavelength used is increased.
In order to overcome this problem, Japanese Patent Laid-Open No. 49936/1997 proposes the provision of I/O (input/output) waveguides for wavelength correction in addition to I/O waveguides of conventional AWGs (arrayed waveguides). In this case, the I/O waveguides are changed according to the correction level of the wavelength.
When the difference in the accuracy of the demultiplexing direction relative to the wavelength difference xcex4xcex is xcex4xcex8, in the arrayed waveguide grating, the center wavelength xcexin can be corrected by a value represented by equation (1) by changing the position of the input waveguides 12, that is, changing the angle xcex8in of incidence on the slab.                               δλ          in                =                              δλ            δθ                    ·                      θ            in                                              (        1        )            
Since, however, the I/O waveguides for wavelength correction are discretely disposed, the degree of correction for the wavelengths is also discrete and, thus, the wavelength cannot be corrected as desired. To provide the degree of wavelength correction as desired, the angle xcex8in of incidence on the slab should be arbitrary.
FIG. 2 shows the construction of an arrayed waveguide grating device for solving the above problem. For example, in this proposal described in xe2x80x9cP. CPU. Clements et al., IEEE, Photon, Tech., Lett., Vol. 7, No. 10, pp. 1040-1041, 1995,xe2x80x9d the substrate is cut at the section 22 of incidence on the slab on the input side of AWG (arrayed waveguides) wafer 21. In the section 22, of incidence on the slab, reinforced with a dolly (glass), an input fiber 24, which is likewise sandwiched by the dolly 23, is bonded (fixed). At the time of the bonding, aligning is directly carried out, and the position of the input fiber 24 is changed as desired according to the degree of wavelength correction.
In general, however, the production error of the input fiber 24 having a spot size is much larger than that of the optical waveguides having a spot size. Therefore, the adoption of this technique raises a problem that a large variation in spot size of the input fiber 24 is causative of a deterioration in characteristics of the arrayed waveguides.
FIG. 3 shows a proposal for solving the above problem. For example, in xe2x80x9cTHE 2000 IEICE (The Institute of Electronics, Information and Communication Engineers) GENERAL CONFERENCE, C-3-76,xe2x80x9d as shown in FIG. 3, the input fiber 31 is connected to the input-side slab waveguide 33 through an optical waveguide 32 for introduction into the slab, rather than bonding of the input fiber 24 at the section 22 of incidence on the slab. Both the input-side slab waveguide 33 and the output-side slab waveguide 34 are provided on an AWG device wafer 35, and a channel waveguides array 36 is provided between and connected to the input-side slab waveguide 33 and the output-side slab waveguide 34. Further, output waveguides 38 are provided between and connected to the output-side slab waveguide 34 and the fiber array 37.
In the case of the arrayed waveguide grating device shown in FIG. 3, the optical waveguide 32 for introduction into the slab is provided between the input fiber 31 and the input-side slab waveguide 33. In this case, waveguides are connected to the input-side slab waveguide 33, and, thus, the problem of a variation in spot size as described above is reduced. Since, however, the optical waveguide 32 for introduction into the slab should be separately provided, this may be an obstacle to mass production.
In the methods shown in FIGS. 2 and 3, the incident section of the slab is cut. Therefore, the generation of an error in the optical axis direction at the slab cut position causes a change in slab length which is causative of a deterioration in wavelength characteristics. Specifically, when the slab has been cut in a larger length than the necessary length, the length can be regulated, for example, by grinding. On the other hand, when the slab length is shorter than the necessary length, the correction per se is impossible.
Further, when module packaging of the device is taken into consideration, the input fiber is preferably parallel to the output fiber. As shown in FIGS. 2 and 3, in order to render the input fiber and the output fiber parallel to each other, the chip layout within the AWG wafer should be changed from a simple one. This is a factor which limits the chip layout within the wafer.
FIG. 4 shows an example of biconnected arrayed waveguides. This construction can be adopted when there is no limitation on chip layout within the wafer. In this drawing, in order to enhance the yield of the arrayed waveguide per wafer to increase the harvest, AWG slabs 41, 42 cross each other, and AWG slabs 43, 44 cross each other to dispose arrayed waveguides 45, 46 in a biconnected form. In this chip layout within the wafer, the yield can be enhanced by selecting an arrayed waveguide having better characteristics from the two arrayed waveguides 45, 46.
In FIG. 4, because, for example, vertically symmetrical arrangement is possible, the AWG slabs 41, 42 can be disposed so as to cross each other while disposing the AWG slabs 43, 44 so as to cross each other, whereby arrayed waveguides 45, 46 are disposed in a biconnected form. On the other hand, the arrayed waveguides in a form as shown in FIGS. 2 and 3 cannot be disposed in a biconnected form without difficulty.
As described above, the conventional arrayed waveguide grating device constructed so as to correct the center wavelength poses problems, for example, a deterioration in characteristics of arrayed waveguides due to a spot size error, the time or labor for providing a specialty wave guide, and the limitation of chip layout.
Although the problems of the arrayed waveguide grating device have been described above, the same problems as involved in the arrayed waveguide grating device are also found in arrayed waveguide modules and optical communication systems using the arrayed waveguide grating device.
Accordingly, it is an object of the invention to provide an arrayed waveguide grating device, which can easily realize wavelength correction, a process for producing the same, and an arrayed waveguide module and an optical communication systems using said arrayed waveguide grating device.
According to the first feature of the invention, an arrayed waveguide grating device comprises: (i) a single or plurality of input waveguides provided on a first substrate; (ii) a first input-side slab waveguide which is connected to the input waveguide and is in such a form that a slab waveguide provided on the first substrate has been cut together with the first substrate at a predetermined position and the first half portion on the first substrate side has been left; (iii) a second input-side slab waveguide which is in such a form that a slab waveguide, identical to said slab waveguide, provided on a second substrate, which is the same or different from the first substrate, has been cut together with the second substrate at said predetermined position and the second half portion on the second substrate side has been left, said second input-side slab waveguide being fixed to the first input-side slab waveguide in such a state that the cut face of the second input-side slab waveguide and the cut face of the first input-side slab waveguide have been relatively moved by a desired degree according to need; (iv) a channel waveguide array which is provided on the second substrate so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment and is connected to the second input-side slab waveguide; (v) an output waveguide provided on the second substrate; and (vi) an output-side slab waveguide which is provided on the second substrate and connects the channel waveguide array to the output waveguide.
According to the first feature of the invention, an input-side slab waveguide provided on an identical substrate is cut into a first input-side slab waveguide and a second input-side slab waveguide which are fixed to each other in such a state that the cut faces have been relatively moved by a desired degree, thereby realizing an arrayed waveguide grating device. Alternatively, a first input-side slab waveguide and a second input-side slab waveguide, each having such a structure that has been formed by the above cutting, are prepared on an identical substrate or respective separate substrates, and the end faces, in the structure such that has been formed by cutting, are fixed to each other in such a state that the cut faces have been relatively moved by a desired degree according to need, thereby realizing an arrayed waveguide grating device. The fixation of the cut or end faces to each other, in such a state that the cut or end faces have been relatively moved by a desired degree in an analog manner, can realize wavelength correction on the input side with high accuracy. Further, since two components are fixed to each other to constitute one arrayed waveguide grating device, the yield can be improved as compared with the case where the arrayed waveguide grating device is produced as a single component.
According to the second feature of the invention, an arrayed waveguide grating device comprises: (i) an input waveguide provided on a first substrate; (ii) a channel waveguide array which is provided on the first substrate constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment; (iii) an input-side slab waveguide which is provided on the first substrate and connects the input waveguide to the channel waveguide array; (iv) a first output-side slab waveguide which is in such a form that a slab waveguide provided on the first substrate and connected to the channel waveguide array has been cut together with the first substrate at a predetermined position and the first half portion on the first substrate side has been left: (v) a second output-side slab waveguide which is in such a form that a slab waveguide, identical to said slab waveguide, provided on a second substrate, which is the same or different from the first substrate, has been cut together with the second substrate at said predetermined position and the second half portion on the second substrate side has been left, said second output-side slab waveguide being fixed to the first output-side slab waveguide in such a state that the cut face of the second output-side slab waveguide and the cut face of the first output-side slab waveguide have been relatively moved by a desired degree according to need; and (vi) a plurality of output waveguides which are provided on the second substrate and are connected to the second output-side slab waveguide.
According to the second feature of the invention, an output-side slab waveguide provided on an identical substrate is cut into a first output-side slab waveguide and a second output-side slab waveguide which are fixed to each other in such a state that the cut faces have been relatively moved by a desired degree, thereby realizing an arrayed waveguide grating device. Alternatively, a first output-side slab waveguide and a second output-side slab waveguide, each having such a structure that has been formed by the above cutting, are prepared on an identical substrate or respective separate substrates, and the end faces, in the structure such that has been formed by cutting, are fixed to each other in such a state that the cut faces have been relatively moved by a desired degree according to need, thereby realizing an arrayed waveguide grating device. The fixation of the cut or end faces to each other, in such a state that the cut or end faces have been relatively moved by a desired degree in an analog manner, can realize wavelength correction on the output side with high accuracy. Further, the selection of various output-side slab waveguides can realize, for example, a change in the number of channels on the output side. Furthermore, since two components are fixed to each other to constitute one arrayed waveguide grating device, the yield can be improved as compared with the case where the arrayed waveguide grating device is produced as a single component.
According to the third feature of the invention, an arrayed waveguide grating device comprising: (i) a single or plurality of input waveguides provided on a first substrate; (ii) a first input-side slab waveguide which is connected to the input waveguide and is in such a form that an input-side slab waveguide provided on the first substrate has been cut together with the first substrate at a predetermined position and the first half portion on the first substrate side has been left; (iii) a second input-side slab waveguide which is in such a form that a slab waveguide, identical to said input-side slab waveguide, provided on a second substrate, which is the same or different from the first substrate, has been cut together with the second substrate at said predetermined position and the second half portion on the second substrate side has been left, said second input-side slab waveguide being fixed to the first input-side slab waveguide in such a state that the cut face of the second input-side slab waveguide and the cut face of the first input-side slab waveguide have been relatively moved by a desired degree according to need; (iv) a channel waveguide array which is provided on the second substrate so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment and is connected to the second input-side slab waveguide; (v) a first output-side slab waveguide which is in such a form that an output-side slab waveguide provided on the second substrate and connected to the channel waveguide array has been cut together with the second substrate at other predetermined position different from said predetermined position and the first half portion on the second substrate side has been left; (vi) a second output-side slab waveguide which is in such a form that a slab waveguide, identical to said output-side slab waveguide, provided on a third substrate, which is the same or different from the second substrate, has been cut together with the third substrate at said other predetermined position and the second half portion on the third substrate side has been left, said second output-side slab waveguide being fixed to the first output-side slab waveguide in such a state that the cut face of the second output-side slab waveguide and the cut face of the first output-side slab waveguide have been relatively moved by a desired degree according to need; and (vii) a plurality of output waveguides which are provided on the third substrate and are connected to the second output-side slab waveguide.
The third feature of the invention comprises a combination of the first feature of the invention, wherein the arrayed waveguide grating device comprises two components divided at the input-side slab waveguide, with the second feature of the invention wherein the arrayed waveguide grating device comprises two components divided at the output-side slab waveguide. That is, the arrayed waveguide grating device according to the third feature of the invention comprises three components in total divided at the input-side slab waveguide and the output-side slab waveguide. These components are fixed to one another in such a manner that the end faces, in such a structure that has been formed by cutting, have been moved by a desired degree according to need, thereby realizing an arrayed waveguide grating device. Therefore, the fixation, in such a state that the end faces in one of or both the two fixation sites have been moved by a desired degree in an analog manner, can realize wavelength correction with high accuracy. Further, the selection of various output-side slab waveguides can realize, for example, a change in the number of output-side ports. Furthermore, since three components are fixed to one another to constitute one arrayed waveguide grating device, the yield can be improved as compared with the case where the arrayed waveguide grating device is produced as a single component. In addition, since the second substrate constituting the channel waveguide array disposed between the input-side slab waveguide and the output-side slab waveguide is required to have higher accuracy than the other substrates, an improvement in yield and a reduction in cost can be realized, for example, by producing only the second substrate according to a production process having high accuracy, producing the first and third substrates according to a production process having relatively low accuracy, and combining these three substrates to constitute one arrayed waveguide grating device.
In arrayed waveguide grating devices according to the first to third features of the invention, the cut site may be a face which has been slightly deviated in a predetermined direction on a three-dimensional space from a face perpendicular to the optical axis.
According to this construction, since the reflecting face is not a face perpendicular to the optical axis, the adverse effect of reflection can be eliminated. Rendering the direction slightly different in a predetermined direction on a three-dimensional space, of course, embraces slight deviation in a two-dimensional direction and hence does not necessarily mean that a three-dimensional direction should be taken.
Further, in arrayed waveguide grating devices according to the first to third features of the invention, preferably the cut site has been reinforced with a dolly.
According to this construction, the use of the reinforcing dolly (glass) can facilitate cutting, polishing, and fixation and, in addition, can maintain the strength after the fixation. It is a matter of course that there is no limitation on the material and the type in the reinforcing member.
In the arrayed waveguide grating device according to the first or second feature of the invention, preferably, the first and second substrates are formed of a material transparent to ultraviolet light.
When an UV-curable resin is used as an adhesive for the fixation, the use of a transparent device substrate material, such as a quartz substrate, that is, a device substrate material having high ultraviolet light transmission, is preferred from the viewpoint of production in consideration of ultraviolet light transmission.
In the arrayed waveguide grating device according to the third feature of the invention, preferably, the first to third substrates are formed of a material transparent to ultraviolet light.
When an UV-curable resin is used as the adhesive, the use of a transparent device substrate material, such as a quartz substrate, that is, a device substrate material having high ultraviolet light transmission, is preferred from the viewpoint of production in consideration of ultraviolet light transmission.
According to the fourth feature of the invention, a process for producing an arrayed waveguide grating device, comprises the steps of: (i) forming, on one substrate, a single or plurality of input waveguides, a plurality of output waveguides, a channel waveguide array constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment, an input-side slab waveguide for connecting the input waveguide to the channel waveguide array, and an output-side slab waveguide for connecting the output waveguide to the channel waveguide array, to produce an arrayed waveguide grating device (arrayed waveguide grating device production step); (ii) cutting the input-side slab waveguide, in the arrayed waveguide grating device produced in the arrayed waveguide grating device production step, integrally with the substrate in a predetermined direction (cutting step); and (iii) fixing the cut faces produced by the cutting step to each other in such a state that the cut faces have been relatively moved in a cut direction by a desired degree (fixation step).
In the production process according to the fourth feature of the invention, the arrayed waveguide grating device according to the first feature of the invention is produced using an identical substrate.
According to the fifth feature of the invention, a process for producing an arrayed waveguide grating device, comprises the steps of: (i) forming, on one substrate, a single or plurality of input waveguides, a plurality of output waveguides, a channel waveguide array constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment, an input-side slab waveguide for connecting the input waveguide to the channel waveguide array, and an output-side slab waveguide for connecting the output waveguide to the channel waveguide array, to produce an arrayed waveguide grating device (arrayed waveguide grating device production step); (ii) cutting the output-side slab waveguide, in the arrayed waveguide grating device produced in the arrayed waveguide grating device production step, integrally with the substrate in a predetermined direction (cutting step): and (iii) fixing the cut faces produced by the cutting step to each other in such a state that the cut faces have been relatively moved in a cut direction by a desired degree (fixation step).
In the production process according to the fifth feature of the invention, the arrayed waveguide grating device according to the second feature of the invention is produced using an identical substrate.
According to the sixth feature of the invention, a process for producing an arrayed waveguide grating device, comprising the steps of: (i) producing a plurality of arrayed waveguide grating devices, each of the plurality of arrayed waveguide grating devices having been produced by forming, on one substrate, a single or plurality of input waveguides, a plurality of output waveguides, a channel waveguide array constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment, an input-side slab waveguide for connecting the input waveguide to the channel waveguide array, and an output-side slab waveguide for connecting the output waveguide to the channel waveguide array (arrayed waveguide grating device production step); (ii) cutting the input-side slab waveguide, in each of the plurality of arrayed waveguide grating devices produced in the arrayed waveguide grating device production step, integrally with the substrate in a predetermined direction (cutting step), into a component having a first cut face and a component having a second cut face; and (iii) selecting a desired combination of a component having a first cut face and a component having a second cut face from the components having a first cut face and the components having a second cut face obtained in the cutting step, and fixing the cut faces of the selected components to each other in such a state that the cut faces have been relatively moved in a cut direction by a desired degree (fixation step).
In the production process according to the sixth feature of the invention, a plurality of substrates, in such a form that an input-side slab waveguide has been divided into a plurality of parts, are previously prepared and are used in proper combination to produce a desired arrayed waveguide grating device.
According to the seventh feature of the invention, a process for producing an arrayed waveguide grating device, comprising the steps of: (i) producing a plurality of arrayed waveguide grating devices, each of the plurality of arrayed waveguide grating devices having been produced by forming, on one substrate, a single or plurality of input waveguides, a plurality of output waveguides, a channel waveguide array constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment, an input-side slab waveguide for connecting the input waveguide to the channel waveguide array, and an output-side slab waveguide for connecting the output waveguide to the channel waveguide array (arrayed waveguide grating device production step); (ii) cutting the output-side slab waveguide, in each of the plurality of arrayed waveguide grating devices produced in the arrayed waveguide grating device production step, integrally with the substrate in a predetermined direction, into a component having a first cut face and a component having a second cut face (cutting step); and (iii) selecting a desired combination of a component having a first cut face and a component having a second cut face from the components having a first cut face and the components having a second cut face obtained in the cutting step, and fixing the cut faces of the selected components to each other in such a state that the cut faces have been relatively moved in a out direction by a desired degree (fixation step).
In the production process according to the seventh feature of the invention, a plurality of substrates, in such a form that an output-side slab waveguide has been divided into a plurality of parts, are previously prepared and are used in proper combination to produce a desired arrayed waveguide grating device.
In the arrayed waveguide grating device according to the second or third feature of the invention, preferably, the second output-side slab waveguide is selectable as desired from second output-side slab waveguides which are different from each other in the number of output waveguides connected thereto,
According to this construction, in connecting the cut second output-side slab waveguide to the first output-side slab waveguide, when a plurality of second output-side slab waveguides different from each other in the number of output waveguides connected thereto are provided, a desired number of ports can be selected therefrom. In this case, the invention can be used for purposes other than the wavelength correction.
In the arrayed waveguide grating device according to the second or third feature of the invention, preferably, the second output-side slab waveguide is constructed as a second output-side slab waveguide such that at least one of output waveguides connected thereto is allocated to a port for monitoring.
According to this construction, in connecting the cut second output-side slab waveguide to the first output-side slab waveguide, when a second output-side slab waveguide, such that at least one of output waveguides connected thereto is allocated to a port for monitoring, is provided, the selection of this output-side slab waveguide permits the invention to be used for purposes other than the wavelength correction.
In the arrayed waveguide grating device according to the first or third feature of the invention, preferably, a plurality of the first substrates, which are different from each other in a part or the whole of the shape of connection of the input waveguide to the first input-side slab waveguide, are provided for selective connection to the second substrate.
According to this construction, a plurality of the first substrates are provided which are different from each other in a part or the whole of the shape of connection of the input waveguide to the first input-side slab waveguide such that the connection has a widened or narrowed shape. In this case, for example, various spectral forms can be selected. Therefore, one substrate can be selected from the plurality of the first substrates and connected to the second substrate to constitute an arrayed waveguide grating device having desired characteristics.
In arrayed waveguide grating device according to the second feature of the invention, a plurality of the second substrates, which are different from each other in a part or the whole of the shape of connection of the output waveguide to the second output-side slab waveguide, are provided for selective connection to the first substrate.
According to this construction, a plurality of the second substrates are provided which are different from each other in a part or the whole of the shape of connection of the output waveguide to the second output-side slab waveguide such that the connection has a widened or narrowed shape. In this case, for example, various spectral forms can be selected. Therefore, one substrate can be selected from the plurality of second substrates and connected to the first substrate to constitute an arrayed waveguide grating device having desired characteristics.
In the arrayed waveguide grating device according to the third feature of the invention, a plurality of the third substrates, which are different from each other in a part or the whole of the shape of connection of the output waveguide to the second output-side slab waveguide, are provided for selective connection to the second substrate.
According to this construction, a plurality of the third substrates are provided which are different from each other in a part or the whole of the shape of connection of the output waveguide to the second output-side slab waveguide such that the connection has a widened or narrowed shape. In this case, for example, various spectral forms can be selected. Therefore, one substrate can be selected from the plurality of third substrates and connected to the second substrate to constitute an arrayed waveguide grating device having desired characteristics.
In the arrayed waveguide grating device according to the first or third feature of the invention, a monitoring input waveguide used for monitoring an output before cutting the input-side slab waveguide into the first input-side slab waveguide and the second input-side slab waveguide is adjacent to the input waveguide and connected to the first input-side slab waveguide and the input waveguide portion other than the monitoring input waveguide is projected toward the input side by a length corresponding to a reduction in the slab length upon cutting of the slab waveguide into the first input-side slab waveguide and the second input-side slab waveguide or polishing of the cut faces.
According to this construction, before cutting, the device can be examined with high accuracy. When the input-side slab waveguide is cut, the length of the slab is reduced at the time of cutting or polishing. In consideration of this, the use of a longer slab length than usual makes it impossible to accurately examine the device before cutting by introducing light into the input-side slab waveguide, due to the long slab length. To overcome this problem, a monitoring input waveguide is previously connected to the slab waveguide in its site having an ordinary slab length. In order to ensure this slab length after cutting, regarding the main input waveguide portion (the input waveguide portion other than the monitoring input waveguide), is projected toward the input side so as to have a slab length which is larger by a length corresponding to a reduction in the slab length upon cutting.
In the embodiment of the arrayed waveguide grating device according to the second or third feature of the invention wherein a second output-side slab waveguide, such that at least one of output waveguides connected thereto is allocated to a port for monitoring, is provided, the monitoring port may be a spectral monitoring port which provides an optical signal of a more steep spectrum than other port connected to the second output-side slab waveguide.
According to this construction, when a port, which provides an optical signal of a more steep spectrum than other port connected to the second output-side slab waveguide, is provided as the spectral monitoring port, the accuracy of the positional correction can be satisfactorily improved, for example, at the time of the fixation of the cutting site of the slab waveguide.
In the embodiment of the arrayed waveguide grating device according to the second or third feature of the invention wherein a second output-side slab waveguide, such that at least one of output waveguides connected thereto is allocated to a port for monitoring, is provided, the monitoring port may be a power monitoring port which obtains an optical signal corresponding a specific port connected to the second output-side slab waveguide to detect the power of the specific port.
According to this construction, the provision of a power monitoring port corresponding to a specific port can realize power monitoring, for example, when measurement with the specific port is impossible.
According to the eighth feature of the invention, an arrayed waveguide grating device comprises: (i) a first substrate on which a single or plurality of input waveguides and a first input-side slab waveguide connected to the input waveguide are disposed and which has a first end face in a region where the input-side slab waveguide has been disposed; and (ii) a second substrate on which a second input-side slab waveguide, a channel waveguide array constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment and connected to the input-side slab waveguide, a plurality of output waveguides, and an output-side slab waveguide for connecting the channel waveguide array to the output waveguide are disposed and which has an end face in a region where the second slab waveguide has been disposed, (iii) said first end face having been fixed to said second end face so that light, which has emerged from the input-side waveguide and entered the first input-side slab waveguide, is optically coupled to the channel waveguide array through the second slab waveguide.
According to this construction, the first end face of the first substrate has been fixed to the second end face of the second substrate so that light, which has emerged from the input-side waveguide and entered the first input-side slab waveguide, is optically coupled to the channel waveguide array through the second slab waveguide. The fixation of these end faces, in such a state that the end faces have been moved according to need, can realize wavelength correction on the input side with high accuracy. Further, since two components are fixed to each other to constitute one arrayed waveguide grating device, the yield can be improved as compared with the arrayed waveguide grating device is produced as a single component.
According to the ninth feature of the invention, an arrayed waveguide module comprises: (i) an arrayed waveguide grating device comprising a single or plurality of input waveguides provided on a first substrate, a first input-side slab waveguide which is connected to the input waveguide and is in such a form that a slab waveguide provided on the first substrate has been cut together with the first substrate at a predetermined position and the first half portion on the first substrate side has been left, a second input-side slab waveguide which is in such a form that a slab waveguide, identical to said slab waveguide, provided on a second substrate, which is the same or different from the first substrate, has been cut together with the second substrate at said predetermined position and the second half portion on the second substrate side has been left, said second input-side slab waveguide being fixed to the first input-side slab waveguide in such a state that the cut face of the second input-side slab waveguide and the cut face of the first input-side slab waveguide have been relatively moved by a desired degree according to need, a channel waveguide array which is provided on the second substrate so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment and is connected to the second input-side slab waveguide, an output waveguide provided on the second substrate, and an output-side slab waveguide which is provided on the second substrate and connects the channel waveguide array to the output waveguide; (ii) an input optical fiber optically connected to the input waveguide; and (iii) an output optical fiber optically connected to the output waveguide.
The ninth feature of the invention provides an arrayed waveguide module using the arrayed waveguide grating device according to the first feature of the invention. According to the construction of the ninth feature of the invention, the wavelength correction on the input side can be carried out with high accuracy. Further, since two components are fixed to each other to constitute one arrayed waveguide grating device, the yield can be improved as compared with the arrayed waveguide grating device is produced as a single component.
According to the tenth feature of the invention, an arrayed waveguide module comprises: (i) an arrayed waveguide grating device comprising a first substrate on which a single or plurality of input waveguides and a first input-side slab waveguide connected to the input waveguide are disposed and which has a first end face in a region where the input-side slab waveguide has been disposed, and a second substrate on which a second input-side slab waveguide, a channel waveguide array constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment and connected to the input-side slab waveguide, a plurality of output waveguides, and an output-side slab waveguide for connecting the channel waveguide array to the output waveguide are disposed and which has an end face in a region where the second slab waveguide has been disposed, said first end face having been fixed to said second end face so that light, which has emerged from the input-side waveguide and entered the first input-side slab waveguide, is optically coupled to the channel waveguide array through the second slab waveguide; (ii) an input optical fiber optically connected to the input waveguide; and (iii) an output optical fiber optically connected to the output waveguide.
The tenth feature of the invention provides an arrayed waveguide module using the arrayed waveguide grating device according the eighth feature of the invention. According to the construction of the tenth feature of the invention, the fixation of the first and second end faces, in such a state that the end faces have been moved according to need, can realize wavelength correction on the input side with high accuracy. Further, since two components are fixed to each other to constitute one arrayed waveguide grating device, the yield can be improved as compared with the arrayed waveguide grating device is produced as a single component.
According to the eleventh feature of the invention, an optical communication system comprises (i) a circular transmission line comprising a plurality of nodes which have been circularly connected through transmission lines, a wavelength division multiplexed optical signal being transmitted through the circular transmission line, each of the nodes comprising: an arrayed waveguide grating device for separating the wavelength division multiplexed optical signal into optical signals of respective wavelengths and an arrayed waveguide grating device for wavelength division multiplexing the separated optical signals of respective wavelengths, (ii) wherein at least one of the arrayed waveguide grating devices comprises a single or plurality of input waveguides provided on a first substrate, a first input-side slab waveguide which is connected to the input waveguide and is in such a form that a slab waveguide provided on the first substrate has been cut together with the first substrate at a predetermined position and the first half portion on the first substrate side has been left, a second input-side slab waveguide which is in such a form that a slab waveguide, identical to said slab waveguide, provided on a second substrate, which is the same or different from the first substrate, has been cut together with the second substrate at said predetermined position and the second half portion on the second substrate side has been left, said second input-side slab waveguide being fixed to the first input-side slab waveguide in such a state that the cut face of the second input-side slab waveguide and the cut face of the first input-side slab waveguide have been relatively moved by a desired degree according to need, a channel waveguide array which is provided on the second substrate so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment and is connected to the second input-side slab waveguide, an output waveguide provided on the second substrate, and an output-side slab waveguide which is provided on the second substrate and connects the channel waveguide array to the output waveguide.
The eleventh feature of the invention provides an optical communication system using the arrayed waveguide grating device according the first feature of the invention. According to the construction of the eleventh feature of the invention, for these arrayed waveguide grating devices, the wavelength correction on the input side can be carried out with high accuracy. Further, since two components are fixed to each other to constitute one arrayed waveguide grating device, as compared with the arrayed waveguide grating device is produced as a single component, the yield can be improved and the cost of the system can be reduced.
According to the twelfth feature of the invention, an optical communication system comprising (i) a circular transmission line comprising a plurality of nodes which have been circularly connected through transmission lines, a wavelength division multiplexed optical signal being transmitted through the circular transmission line, each of the nodes comprising: an arrayed waveguide grating device for separating the wavelength division multiplexed optical signal into optical signals of respective wavelengths and an arrayed waveguide grating device for wavelength division multiplexing the separated optical signals of respective wavelengths, (ii) wherein at least one of the arrayed waveguide grating devices comprises a first substrate on which a single or plurality of input waveguides and a first input-side slab waveguide connected to the input waveguide are disposed and which has a first end face in a region where the input-side Blab waveguide has been disposed, and a second substrate on which a second input-side slab waveguide, a channel waveguide array constructed so as for waveguides constituting the channel waveguide array to respectively have successively increased lengths in a predetermined waveguide length increment and connected to the input-side slab waveguide, a plurality of output waveguides, and an output-side slab waveguide for connecting the channel waveguide array to the output waveguide and disposed and which has an end face in a region where the second slab waveguide has been disposed, said first end face having been fixed to said second end face so that light, which has emerged from the input-side waveguide and entered the first input-side slab waveguide, is optically coupled to the channel waveguide array through the second slab waveguide.
The twelfth feature of the invention provides an optical communication system using the arrayed waveguide grating device according to the eighth feature of the invention. According to the construction of the twelfth feature of the invention, for these arrayed waveguide grating devices, the wavelength correction on the input side can be carried out with high accuracy. Further, in these arrayed waveguide grating devices, since two components are fixed to each other to constitute one arrayed waveguide grating device, as compared with the arrayed waveguide grating device is produced as a single component, the yield can be improved and the cost of the system can be reduced.